探討金屬有機框架材料其配位分子對於甲烷吸附量與吸附位向的影響

Abstract

為了瞭解不同配位分子的MOFs材料對甲烷吸附位置與吸附量的影響，我們利用巨正則蒙地卡羅方法(GCMC)計算298K下甲烷分別於配位分子含三反應官能基數的HKUST-1、ZJU-36以及配位分子含四反應官能基數的NOTT-100、NOTT-101以及NOTT-102之恆溫吸附曲線與吸附位置。我們發現甲烷於此五種MOFs材料中的吸附作用利主要來自於苯環及金屬簇，其中在三反應官能基方面，儘管ZJU-36的DPS、GSA以及SPV皆比HKUST-1大，但由於骨架擴大的同時，苯環與金屬簇數量並沒有增加，增加的僅為對甲烷有較弱吸引力的碳鏈(C=C)，因此甲烷數量增加的幅度有限，此外我們再將晶格體積因素考慮進去時，會導致最後由吸附個數換算成吸附量(v/v)時，ZJU-36呈現下降的趨勢。另外在四反應官能基方面，三者的DPS、GSA以及SPV皆為NOTT-102> NOTT-101> NOTT-100，但吸附曲線的趨勢在35Bar以下以NOTT-100為最高，35Bar以上則以NOTT-101為最高，主要原因是在低壓下，其實苯環數量的不同對甲烷吸附量的影響不大，但隨著壓力的增加，由於NOTT-101及NOTT-102的配位分子上苯環個數較多，甲烷會開始於苯環附近大幅增加。由以上的研究我們也認為在未來的MOF材料設計上，如果需要藉由擴大MOF的DPS、GSA以及SPV來填充甲烷，增加苯環數量的方式會比延長碳鏈的方式來的有效，我們深信這樣的結果可以為新型高性能MOFs的合成提供設計構想，促進MOFs材料的發展以及應用。

In this study, we employ simulation methods to calculate the adsorption capacity and predict the orientation of methane of five metal organic frameworks (MOFs). The MOFs which we choose is based on the same metal cluster, symmetry and number of functional groups but they are different from linkers. Then we explore the correlation among the adsorption capacity, the orientation and varying linkers. First, We find that methane adsorbed in HKUST-1 and ZJU-36 is influenced by metal cluster and benzene rings. As the DPS, GSA and SPV increase, the number of carbon chains which have weak impact on methane increase. Therefore the number of methane increases slightly. And if we take the cell volume into consideration, the capacity value of ZJU-36 will decrease significantly. In addition, as for NOTT series, methane is also influenced by metal cluster and benzene rings. And as the DPS, GSA and SPV increase, the rank of adsorption capacity does not increase as expected. After systematic research, we realize the reason why the rank is different below and exceed 35Bar is the number of benzene rings in consideration of cell volume. To sum up, we think if scientists want to synthesize MOFs with larger DPS, GSA and SPV, the increment of benzene rings will be a better choice. We hope this research can provide good design concept for MOFs in the future to improve adsorption capacity.